Alternatively powered vehicles such as hybrid electric vehicles, plug-in hybrid electric vehicles and battery electric vehicles may use an electric machine to convert energy stored in a high-voltage battery to motive power. For hybrid electric vehicles, the high-voltage battery may store energy converted by an internal combustion engine or captured from regenerative braking events. The high-voltage battery of plug-in hybrid electric vehicles may additionally store energy received from a utility grid. Likewise, the high-voltage battery of battery electric vehicles may store energy received from a utility grid.
Certain of the above energy sources may have a cost associated with them. An internal combustion engine of a hybrid electric vehicle, for example, may burn gasoline to convert energy for storage by the high-voltage battery. This gasoline, of course, must be purchased. Utility grids likewise charge for the electric power they supply. The energy captured from regenerative braking events, in contrast, does not have such a direct cost. In a sense, it is free energy. It may thus be desirable to charge a high-voltage battery of an alternatively powered vehicle with energy that does not impose a direct cost on the driver.